Conventionally, oil and the like produced from an offshore seabed oil field are conveyed to a floating oil production facility by a flexible tube for fluid transport. An internal-pressure-resistant characteristic, a fluid-tight property, waterproof property and the like are required for the flexible tube.
For such a flexible tube for fluid transport, for example, an interlocked tube made of stainless steel, which is excellent in flexibility, in external pressure-resistant reinforcement and in lateral pressure-resistant reinforcement at the time of installation, is used for an innermost layer. A plastic inner tube which is excellent in oil proof property and in fluid-tight property is provided to the outer periphery of the innermost layer. A metallic internal-pressure-resistant reinforcing layer for internal-pressure-resistant reinforcement and a metallic axial-force reinforcing layer for the axial direction reinforcement are further provided to its outer periphery. A plastic sheath as a waterproof layer is provided to the outermost layer (Patent document 1).